1. Field of the Invention
The present invention relates to a method and an apparatus for forming a glass layer on the surface of a workpiece, a method and an apparatus for forming a metal layer on the surface of a workpiece, and an electronic component manufacturing method.
2. Description of the Related Art
Generally, electronic components such as chip-type coils, in which spiral conductive patterns are provided on ferrite cores, are provided with glass layers thereon as a protective coating prior to forming conductive patterns thereon. Such electronic components have enhanced environmental resistance and insulation performance, and are protected from the penetration of plating solutions when the electronic component is being plated.
Conventionally, in order to provide a glass layer on a ferrite core, (1) a method in which a glass layer is provided by immersing a ferrite core into a glass paste (or a glass slurry) composed of a glass powder, a binder resin, and a solvent, and firing the ferrite core, (2) a method in which a glass layer is provided by applying a glass paste onto the ferrite core by screen printing and firing the ferrite core, and other similar methods are known in the art.
To form a conductive pattern on a ferrite core, (3) a method in which a conductive pattern is formed by providing a metal layer pattern on a ferrite core by screen-printing a conductive paste including a metal powder, and firing the ferrite core, (4) a method in which a conductive pattern is formed by drying a green metal layer obtained by immersing the ferrite core in a conductive paste including a metal powder and/or glass powder, firing the green metal layer, and patterning the fired metal layer, (5) a method in which a conductive pattern is provided by forming a metal layer via electroless plating and patterning the metal layer, and other similar methods are known in the art.
As for the conventional methods of forming a glass layer on a ferrite core, in method (1), it is difficult to provide a glass layer having a uniform thickness on the surface of the ferrite core, and, in addition, a glass layer cannot be formed on the portion of the surface which is blocked by the ferrite core holder. In method (2), since screen-printing must be performed on each surface of the ferrite core, the screen-printing step must be performed multiple times, resulting in reduced productivity and increased costs. When the surface of the ferrite core has irregularities, it is difficult to form a glass layer having a uniform thickness thereon.
Japanese Patent Unexamined Application Publication No. 8-222411 discloses a method for forming a glass layer on the surface of a workpiece such as a ferrite core. The method includes the steps of preparing glass granules by adding a binder resin to a glass powder and heat-treating the glass granules together with chip-type workpieces (basic electronic components) while mixing the granules and the workpieces in a rotating thermostable container.
However, in this method, when the glass powder has high viscosity or when a crystallized glass powder is used as a glass powder, it becomes difficult to uniformly mix the workpieces and the granules, and, consequently, the thickness of the glass layers is likely to be non-uniform. Furthermore, the workpieces may clump and stick to the inner wall of the container, decreasing the manufacturing efficiency.
As for the conventional methods for forming a conductive pattern on a ferrite core, in method (3), since the screen-printing must be performed on each surface of the ferrite core, the screen-printing is performed a number of times, resulting in reduced productivity and increased costs. Also, when the surface of the ferrite core has irregularities, it is difficult to form a metal layer having a uniform thickness thereon. In method (4), it is difficult to form a green metal layer having uniform thickness on the surface of the ferrite core, and the green metal layer cannot be formed on the portion of the surface which is blocked by the ferrite core holder.
In method (5), the surface of the ferrite core needs to be pretreated, and it is generally difficult to form a thick layer thereon. Furthermore, because plating solutions are used, the problem of effluent disposal exists, and reliability of the product is reduced due to the penetration of the plating solutions.
To overcome the above-described problems, preferred embodiments of the present invention provide a method and an apparatus in which a homogeneous glass layer of uniform thickness is efficiently formed on the surface of a workpiece, such as a ferrite core. Another preferred embodiment of the present invention provides a method of manufacturing an electronic component having a homogeneous glass layer of uniform thickness provided on the surface thereof and which exhibits superior environmental resistance and superior insulation performance.
Still another preferred embodiment of the present invention provides a method and an apparatus in which a homogenous metal layer of uniform thickness is efficiently formed on the surface of a workpiece such as a ferrite core.
Yet another preferred embodiment of the present invention provides a method of manufacturing an electronic component, the electronic component in which a homogeneous metal layer of uniform thickness is formed on the surface thereof and which is highly reliable.
A method for forming a glass layer according to the first preferred embodiment of the present invention includes the steps of placing a workpiece in a rotatable container, spraying a glass slurry onto the workpiece to form a green glass layer on the surface of the workpiece while rotating the container, and heating the workpiece in the rotating container so as to dry the green glass layer.
By using this method, a homogeneous glass layer having a uniform thickness is efficiently formed on the surface of the workpiece.
According to the second preferred embodiment of the present invention, an apparatus for forming a glass layer includes a rotatable container, a slurry discharger for spraying a glass slurry onto a workpiece disposed in the container to form a green glass layer on the surface of the workpiece, and a heating unit for heating the workpiece so as to dry the green glass layer formed thereon.
By using this apparatus, consistency in the above-described method for forming a glass layer according to the first preferred embodiment of the invention is greatly enhanced.
According to the third preferred embodiment of the present invention, a method for manufacturing an electronic component (hereinafter referred to as the xe2x80x9cfirst electronic component manufacturing methodxe2x80x9d) is provided in which a glass layer is formed on a basic electronic component by using the method for forming a glass layer according to the first preferred embodiment of the present invention.
By using this manufacturing method, an electronic component which has a homogeneous glass layer of uniform thickness on the surface thereof and which exhibits superior environment resistance and insulation performance is efficiently manufactured.
According to the fourth preferred embodiment of the present invention, a method for forming a metal layer includes the steps of placing a workpiece in a rotatable container, spraying a metal slurry onto the workpiece to form a green metal layer on the surface of the workpiece while rotating the container, and heating the workpiece in the rotating container so as to dry the green metal layer.
By using this method, a homogeneous metal layer of uniform thickness is efficiently formed on the surface of the workpiece.
According to the fifth preferred embodiment of the present invention, an apparatus for forming a metal layer includes a rotatable container, a slurry discharger for spraying a metal slurry onto a workpiece disposed in the container to form a green metal layer on the surface of the workpiece, and a heating unit for heating the workpiece so as to dry the green metal layer.
By using this apparatus, consistency in the above-described method for forming a metal layer according to the fourth preferred embodiment of the invention is greatly enhanced.
According to a sixth preferred embodiment of the present invention, a method of manufacturing an electronic component (hereinafter referred to as the xe2x80x9csecond electronic component manufacturing methodxe2x80x9d) is provided, in which a metal layer is formed on a basic electronic component by the method of forming a metal layer according to the fourth preferred embodiment of the present invention.
By using this manufacturing method, an electronic component which has a homogeneous metal layer of uniform thickness on the surface thereof and which is highly reliable is efficiently manufactured.
Other features, elements, characteristics and advantages of present invention will become apparent from the following detailed description of preferred embodiments thereof with reference to the attached drawings.